In people with an overactive bladder (OAB), the detrusor muscle
(layered smooth muscle that surrounds the bladder) contracts spastically,
sometimes without a known cause, which results in sustained, high bladder
pressure and the urgent need to urinate (called urgency). Normally, the detrusor
muscle contracts and relaxes in response to the volume of urine in the bladder
and the initiation of urination.
People with OAB often experience urgency at inconvenient and unpredictable
times and sometimes lose control before reaching a toilet. Thus, overactive
bladder interferes with work, daily routine, and intimacy; causes embarrassment;
and can diminish self-esteem and quality of life.
Click here to complete the OAB questionnaire.
Urination (micturition) involves processes within the urinary tract and the
brain. The slight need to urinate is sensed when urine volume reaches about
one-half of the bladder's capacity. The brain suppresses this need until a
person initiates urination.
Once urination has been initiated, the nervous system signals the detrusor
muscle to contract into a funnel shape and expel urine. Pressure in the bladder
increases and the detrusor muscle remains contracted until the bladder empties.
Once empty, pressure falls and the bladder relaxes and resumes its normal shape.
Incidence and Prevalence
Overactive bladder affects men and women equally. The U.S. Department of
Health and Human Services has reported that approximately 13 million people in
the United States suffer from OAB and other forms of incontinence.
Malfunctioning detrusor muscle in the smooth muscle of the bladder causes
overactive bladder. Identifiable underlying causes include the following:
- Nerve damage caused by abdominal trauma, pelvic trauma, or surgery
- Bladder stones
- Drug side effects
- Neurological disease (e.g., multiple sclerosis, Parkinson's disease,
stroke, spinal cord lesions)
Other conditions can produce symptoms similar to those experienced with
overactive bladder, the most common of which is urinary tract infection (UTI) in
Signs and Symptoms
Three symptoms are associated with an overactive bladder:
- Frequency (frequent urination)
- Urgency (urgent need to urinate)
- Urge incontinence (strong need to urinate followed by leaking or
involuntary and complete voiding)